全文获取类型
收费全文 | 1498676篇 |
免费 | 31902篇 |
国内免费 | 9445篇 |
专业分类
电工技术 | 36700篇 |
技术理论 | 10篇 |
综合类 | 10249篇 |
化学工业 | 262385篇 |
金属工艺 | 66445篇 |
机械仪表 | 44093篇 |
建筑科学 | 47524篇 |
矿业工程 | 13244篇 |
能源动力 | 51544篇 |
轻工业 | 106927篇 |
水利工程 | 15607篇 |
石油天然气 | 40437篇 |
武器工业 | 661篇 |
无线电 | 200944篇 |
一般工业技术 | 279670篇 |
冶金工业 | 156156篇 |
原子能技术 | 34485篇 |
自动化技术 | 172942篇 |
出版年
2021年 | 16692篇 |
2020年 | 13524篇 |
2019年 | 16080篇 |
2018年 | 16276篇 |
2017年 | 15834篇 |
2016年 | 22393篇 |
2015年 | 19619篇 |
2014年 | 31534篇 |
2013年 | 91071篇 |
2012年 | 38078篇 |
2011年 | 49603篇 |
2010年 | 44860篇 |
2009年 | 53410篇 |
2008年 | 46164篇 |
2007年 | 43044篇 |
2006年 | 46947篇 |
2005年 | 40976篇 |
2004年 | 42445篇 |
2003年 | 41406篇 |
2002年 | 39134篇 |
2001年 | 35725篇 |
2000年 | 33708篇 |
1999年 | 33477篇 |
1998年 | 41501篇 |
1997年 | 36588篇 |
1996年 | 32914篇 |
1995年 | 30422篇 |
1994年 | 28595篇 |
1993年 | 28238篇 |
1992年 | 25792篇 |
1991年 | 22831篇 |
1990年 | 23209篇 |
1989年 | 22032篇 |
1988年 | 20498篇 |
1987年 | 18766篇 |
1986年 | 18186篇 |
1985年 | 21522篇 |
1984年 | 21852篇 |
1983年 | 19762篇 |
1982年 | 18887篇 |
1981年 | 18955篇 |
1980年 | 17519篇 |
1979年 | 18111篇 |
1978年 | 17404篇 |
1977年 | 16916篇 |
1976年 | 17512篇 |
1975年 | 15672篇 |
1974年 | 15231篇 |
1973年 | 15280篇 |
1972年 | 12857篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Joseph O'Donnell Pierre-André Cazade Sarah Guerin Ahmed Djeghader Ehtsham Ul Haq Kai Tao Ehud Gazit Eiichi Fukada Christophe Silien Tewfik Soulimane Damien Thompson Syed A. M. Tofail 《Advanced functional materials》2021,31(28):2100884
Controlling the electromechanical response of piezoelectric biological structures including tissues, peptides, and amino acids provides new applications for biocompatible, sustainable materials in electronics and medicine. Here, the piezoelectric effect is revealed in another class of biological materials, with robust longitudinal and shear piezoelectricity measured in single crystals of the transmembrane protein ba3 cytochrome c oxidase from Thermus thermophilus. The experimental findings from piezoresponse force microscopy are substantiated using a range of control measurements and molecular models. The observed longitudinal and shear piezoelectric responses of ≈ 2 and 8 pm V−1, respectively, are comparable to or exceed the performance of commonly used inorganic piezoelectric materials including quartz, aluminum nitride, and zinc oxide. This suggests that transmembrane proteins may provide, in addition to physiological energy transduction, technologically useful piezoelectric material derived entirely from nature. Membrane proteins could extend the range of rationally designed biopiezoelectric materials far beyond the minimalistic peptide motifs currently used in miniaturized energy harvesters, and the finding of robust piezoelectric response in a transmembrane protein also raises fundamental questions regarding the molecular evolution, activation, and role of regulatory proteins in the cellular nanomachinery, indicating that piezoelectricity might be important for fundamental physiological processes. 相似文献
992.
Liangtao Yang Liang-Yin Kuo Juan Miguel López del Amo Prasant Kumar Nayak Katherine A. Mazzio Sebastian Maletti Daria Mikhailova Lars Giebeler Payam Kaghazchi Teófilo Rojo Philipp Adelhelm 《Advanced functional materials》2021,31(38):2102939
A known strategy for improving the properties of layered oxide electrodes in sodium-ion batteries is the partial substitution of transition metals by Li. Herein, the role of Li as a defect and its impact on sodium storage in P2-Na0.67Mn0.6Ni0.2Li0.2O2 is discussed. In tandem with electrochemical studies, the electronic and atomic structure are studied using solid-state NMR, operando XRD, and density functional theory (DFT). For the as-synthesized material, Li is located in comparable amounts within the sodium and the transition metal oxide (TMO) layers. Desodiation leads to a redistribution of Li ions within the crystal lattice. During charging, Li ions from the Na layer first migrate to the TMO layer before reversing their course at low Na contents. There is little change in the lattice parameters during charging/discharging, indicating stabilization of the P2 structure. This leads to a solid-solution type storage mechanism (sloping voltage profile) and hence excellent cycle life with a capacity of 110 mAh g-1 after 100 cycles. In contrast, the Li-free compositions Na0.67Mn0.6Ni0.4O2 and Na0.67Mn0.8Ni0.2O2 show phase transitions and a stair-case voltage profile. The capacity is found to originate from mainly Ni3+/Ni4+ and O2-/O2-δ redox processes by DFT, although a small contribution from Mn4+/Mn5+ to the capacity cannot be excluded. 相似文献
993.
Automation and Remote Control - We study the resource management problem in an aggregated data access system on the example of a cloud storage designed to manage data from medium and small... 相似文献
994.
Wireless Personal Communications - In recent years, the emergence of Internet of things and cyber-physical system provide a proactive and efficacious solution to enable remote monitoring, machine... 相似文献
995.
Wireless Personal Communications - This paper summarizes the ongoing research initiatives based on the advanced multiple access techniques towards the fifth generation (5G) wireless communication... 相似文献
996.
Bagraev N. T. Kukushkin S. A. Osipov A. V. Romanov V. V. Klyachkin L. E. Malyarenko A. M. Khromov V. S. 《Semiconductors》2021,55(2):137-145
Semiconductors - A cycle of experimental investigations is carried out, specifically, the measurements and analysis of field dependences of the static magnetic susceptibility in samples of... 相似文献
997.
Journal of Engineering Physics and Thermophysics - A hybrid model has been developed for the analysis of the process of combined mass and heat transfer in closed rectangular cavities under the... 相似文献
998.
Skoblo T. S. Klochko O. Yu. Sidashenko O. I. Belkin I. L. Avtukhov A. K. Maltsev T. V. Deryabkina E. S. Kolpachenko N. M. 《Materials Science》2021,56(6):771-778
Materials Science - We study the causes and signs of degradation of cementite in chromium-nickel cast iron used for the production of massive forming rolls and the specific features of structural... 相似文献
999.
1000.
M. Aamir I. Bibi S. Ata K. Jilani F. Majid S. Kamal N. Alwadai M.A.S. Raza M. Bashir S. Iqbal M. Aadil M. Iqbal 《Ceramics International》2021,47(12):16696-16707
In the present investigation, La1-xCoxCr1-yFeyO3 (x,y = 0.0, 0.12, 0.36, 0.60) perovskite was fabricated via a facile micro-emulsion route. The synthesized perovskites were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) techniques to examine the effect of Co and Fe ions on the physico-chemical properties. The ferroelectric, dielectric, and magnetic properties of La1-xCoxCr1-yFeyO3 were changed significantly as a function of dopants contents (Co and Fe ions). Outcomes revealed that the dielectric, ferroelectric and magnetic properties of LaCrO3 perovskite can be tuned significantly via Co and Fe doping and La0.40Co0.60Cr0.40Fe0.60O3 have potential for photocatalytic dye removal under (visible) light expoure. The photocatalytic activity (PCA) of the pristine LaCrO3 and La0.40Co0.60Cr0.40Fe0.60O3 photocatalyst was evaluated under (visible) light irradiation for crystal violet (CV) dye. Experimental results revealed that La0.40Co0.60Cr0.40Fe0.60O3 photocatalyst degrdae almost 77.21% CV dye with the rate constant value of 0.01475 min?1. In the presence of isopropyl alcohol (IPA) scavenger, the PCA of the La0.40Co0.60Cr0.40Fe0.60O3 photocatalyst and rate constant value of the photocatalytic reaction decreased to 32.5% and 0.00491 min?1, suggesting the superoxide as main active specie. Results revealed that Co and Fe doping doped material is efficient for photocatalytic presentations under solar light expoure. 相似文献